Showing papers on "Electric field published in 1990"
TL;DR: The growth of ramified metallic deposits by electrodeposition from dilute salt solutions and in a high electric field has been considered in the geometry of a thin rectangular cell and it is found that ramified growth is a direct consequence of the creation of a space charge upon anion depletion in the vicinity of the cathode.
Abstract: The growth of ramified metallic deposits by electrodeposition from dilute salt solutions and in a high electric field has been considered in the geometry of a thin rectangular cell. The equations governing ion motion in the case of a dilute electrolyte have been solved numerically and analytically in a one-dimensional (1D) and a 2D approximation. It is found that ramified growth is a direct consequence of the creation of a space charge upon anion depletion in the vicinity of the cathode. The front of the ramified deposit is predicted to advance at a speed just equal to the velocity of the anions in the applied electric field. The presence of this space charge ahead of the growing front is associated with a potential drop \ensuremath{\delta}V. Resolution of the equations in the 2D case shows that the dense-parallel morphology of the deposit also results quite naturally from the existence of a space charge in the vicinity of the filament tips. The average filament spacing and sidebranch tilting angle can be directly related to the values of \ensuremath{\delta}V and of the applied electric field. The mechanism giving rise to the space charge will apply as well to any physical system involving electric conduction with two types of carriers, if one of them exhibits blocking-contact characteristics.
925 citations
TL;DR: In this article, the authors used a differential mobility classifier with a condensation nuclei counter as a detector to measure the electric field strength of a single particle in a time-varying electric field.
Abstract: The measurement of particle size distributions using electrical mobility can be accelerated significantly by an alternate mode of operating mobility instruments. Rather than changing the electric field in discrete steps to select particles in a given mobility range, the electric field can be scanned continuously. The particles are classified in a time-varying electric field, but for an exponential ramp in the field strength there remains a one-to-one correspondence between the time a particle enters the classifier and the time it leaves. By this method, complete scans of mobility with as many as 100 mobility measurements have been made in 30 seconds using a differential mobility classifier with a condensation nuclei counter as a detector.
854 citations
TL;DR: In this article, the dynamics of charge recombination following electron injection from the excited state of RuL{sub 3} into the conduction band of the semiconductor were examined under potentiostatic control of the electric field within the space charge layer of the membrane.
Abstract: Transparent titanium dioxide membranes (thickness 2.7 {mu}m) were prepared by sintering of 8-nm colloidal anatase particles on a conducting glass support. The dynamics of charge recombination following electron injection from the excited state of RuL{sub 3} (L = 2,2{prime}-bipyridine-4,4{prime}-dicarboxylic acid) into the conduction band of the semiconductor were examined under potentiostatic control of the electric field within the space charge layer of the membrane. Biasing the Fermi level of the TiO{sub 2} positive of the flat-band potential sharply reduced the recombination rate, a 1,000-fold decrease being associated with a potential change of only 300 mV. Photoelectrochemical experiments performed with the same RuL{sub 3}-loaded membrane in NaI-containing water show the onset of anodic photocurrent to occur in the same potential domain. Forward biasing of the membrane potential impairs photosensitized charge injection turning on the photoluminescence of the adsorbed sensitizer.
693 citations
TL;DR: In this article, the rate of the resistance degradation of doped SrTiO3 ceramics is investigated as a function of various external and material parameters, including voltage, electric field, and thickness of the dielectric.
Abstract: The rate of the resistance degradation of doped SrTiO3 ceramics is investigated as a function of various external and material parameters. The effects of the mutually interrelated parameters dc voltage, dc electric field, and thickness of the dielectric are described by power laws. Electron microscopic potential contrast studies show a Maxwell-Wagner polarization leading to a concentration of the electric field at the grain boundaries during the degradation. Based on this finding, the voltage step per grain boundary, ΔΘgb, is introduced as a rate-determining parameter which allows an explanation of the influence of the grain size on the degradation rate as well as the difference in the power laws for ceramic and single-crystal samples.
602 citations
TL;DR: In this article, the effects of a static or dynamic electric field upon electronic motion in a molecule have been studied in terms of multipolar electronic polarizabilities and higher-order hyperpolarizabilities.
Abstract: For many years the effects of a static or dynamic electric field upon electronic motion in a molecule have been studied. These effects have been described in terms of multipolar electronic polarizabilities and higher-order hyperpolarizabilities. Much less attention, however, has been paid to the effects of an electric field upon vibrational and rotational motion. It is the aim of this review to consider, in some detail, these effects. As in the electronic work, they too will be described in terms of polarizabilities and hyperpolarizabilities (the latter being particularly important for the study of nonlinear optics). The theory will be developed so as to bring together the different methods that have been used in various calculations. Examples drawn from the recent literature will be discussed and it will be seen that in many cases vibrational and rotational changes with an electric field are as important as electronic ones, if not more so. Examples of experimental work relevant to this review include research on the Kerr effect, electric-field-induced second-harmonic generation, and third-harmonic generation.
422 citations
TL;DR: A nonlinear Hodgkin-Huxley cable model describes the response of the nerve fiber to this induced electric field and predicts complicated dynamics such as action potential annihilation and dispersion.
Abstract: A model is presented to explain the physics of nerve stimulations by electromagnetic induction. Maxwell's equations predict the induced electric field distribution that is produced when a capacitor is discharged through a stimulating coil. A nonlinear Hodgkin-Huxley cable model describes the response of the nerve fiber to this induced electric field. Once the coil's position, orientation, and shape are given and the resistance, capacitance, and initial voltage of the stimulating circuit are specified, this model predicts the resulting transmembrane potential of the fiber as a function of distance and time. It is shown that the nerve fiber is stimulated by the gradient of the component of the induced electric field that is parallel to the fiber, which hyperpolarizes or depolarizes the membrane and may stimulate an action potential. The model predicts complicated dynamics such as action potential annihilation and dispersion. >
407 citations
TL;DR: Electropermeabilization is studied in terms of flow of diffusing molecules between cells and external medium and direct quantification of the phenomenon shows that electric field intensity is a critical parameter in the induction of permeabilization.
383 citations
TL;DR: A physical model in which cells are considered as possible detectors of very weak periodic electric fields yields a general relation between cell size and both thermally induced fluctuations in membrane potential and the maximum change in membranes potential caused by an applied field.
Abstract: A physical model in which cells are considered as possible detectors of very weak periodic electric fields yields a general relation between cell size and both thermally induced fluctuations in membrane potential and the maximum change in membrane potential caused by an applied field. The simplest version of the model provides a broad-band estimate of the smallest applied electric field to which membrane macromolecules can directly respond (about 10(-3) volt per centimeter). Much smaller fields (10(-6) volt per centimeter) can be detected if there is a response in only a narrow band of frequencies or if signal averaging occurs through field-induced variation in the catalytic activity of membrane-associated enzymes. Both extensions of the simplest version remove the apparent violation of the thermal noise limit found in some experiments.
333 citations
TL;DR: In this article, the authors present the theoretical foundation of a novel technique for the orientation of ∑-molecules and symmetric tops with permanent electric dipole moment, based on the adiabatic transformation of free rotational states into those of librational oscillations taking place during the passage of a molecule into a strong electric field.
Abstract: We present the theoretical foundation of a novel technique for the orientation of ∑‐molecules and symmetric tops with permanent electric dipole moment. The method bases on the adiabatic transformation of free rotational states into those of librational oscillations taking place during the passage of a molecule into a strong electric field. Several examples of calculated spatial distributions of the molecular axis are given. The computational results demonstrate that in connection with highly relaxed supersonic nozzle beams only moderately strong electric fields are required to generate a marked orientation of the axis. In a first application of this technique we studied steric effects of the reaction K+CH3I→KI+CH3 at two elevated collision energies (0.79 and 1.24 eV). All observed steric effects could be rationalized in terms of a simple impulsive reaction model. We find that backward scattered products are more likely formed if the approaching atoms face the I‐end of CH3I—in agreement with low energy results—while forward scattered products are favorably formed if the CH3‐end is encountered.
310 citations
TL;DR: In this paper, the deformation of acrylic acid-acrylamide copolymer gels in an aqueous solution under the influence of a dc electric field was studied.
Abstract: Deformation of acrylic acid–acrylamide copolymer gels in an aqueous solution under the influence of a dc electric field was studied. In the electric field, the gel swells, shrinks, or bends. It depends on the concentration of polyion coo− in the gel. When the concentration is low, the gel shrinks, and, when high, it swells. The gel which does not contain polyion is not influenced by the electric field. The long and thin gel is bent in an arc. The bent gel can be recovered to the original shape by removing the applied electric field or by changing the polarity of the applied electric field. The deformation is closely related to two substantial changes. One is the change of the osmotic pressure caused by the ion concentration difference between the inside and the outside of a gel. The other is the conformational change of the polymer network with decreasing of the polyion concentration.
256 citations
01 Apr 1990
TL;DR: In this article, the shear of the radial electric field and poloidal rotation velocity in the {ital H} mode was localized within the order of an ion poloidal gyroradius near the separatrix, in the region of ion collisionality.
Abstract: The structure of the edge radial electric field {ital E}{sub {ital r}} inferred from the poloidal rotation velocity is compared with that of the particle and thermal transport barrier for {ital H}-mode plasmas in JFT-2M. Both {ital E}{sub {ital r}} and its gradient {partial derivative}{ital E}{sub {ital r}}/{partial derivative}{ital r} in the thermal transport barrier are found to become more negative at the {ital L}-{ital H} transition. On the other hand, {partial derivative}{ital E}{sub {ital r}}/{partial derivative}{ital r} is more positive outside of the separatrix. The shear of the radial electric field and poloidal rotation velocity in the {ital H} mode is localized within the order of an ion poloidal gyroradius near the separatrix, in the region of ion collisionality {nu}{sub *{ital i}}{approx}20--40.
TL;DR: In this article, the authors explore three methods to account for fast, nonequilibrium electrons: the single-beam method, the multibeam method, and particle (Monte Carlo) simulations.
Abstract: Mathematical models of dc glow discharges sustained by electrons emitted by the cathode and accelerated into the cathode fall must take into account the highly nonequilibrium nature of these fast electrons. However, the electric field profile through the discharge is determined mainly by the distribution of ions and slow electrons. In this paper we explore three methods to account for fast, nonequilibrium electrons: the single-beam method, the multibeam method, and particle (Monte Carlo) simulations. Ions and cold electrons are treated using equations of change assuming collisionally dominated motion (i.e., drift and diffusion), and the self-consistent electric field is determined by solving these equations simultaneously with Poisson's equation. Creation rates for ions and slow electrons are obtained from the fast-electron models. Simulation results indicate that, although the single-beam model is qualitatively correct, it is hampered by its sensitivity to assumptions in the numerical approach, and its tendency to predict negative voltage-current characteristics at low pressures and high voltages, which are not evident in results from the higher-order multibeam model. Although an improvement over the single-beam model, comparison with experimental optical-emission measurements reveals that the multibeam model predicts excitation profiles that extend too far into the discharge. Accurate comparisons are possible with particle simulations, which incorporate angular scattering of fast electrons.
TL;DR: In this article, an improved return stroke model that is both physically oriented and has a relatively straightforward mathematical basis is proposed, where the current at the channel base is specified, and a time-dependent discharging of the charge stored on the leader channel determines the channel current as a function of height and time.
Abstract: An improved return stroke model that is both physically oriented and has a relatively straightforward mathematical basis is proposed. The current at the channel base is specified, and a time-dependent discharging of the charge stored on the leader channel determines the channel current as a function of height and time. The discharging process is separated into (1) the exponential discharge of the leader head and leader core with a relatively short time constant, less than 1 μs, which we call the “breakdown” time constant, and (2) the exponential discharge of the charge stored around the leader core with a longer time constant, of the order of microseconds. If a typical measured channel-base current is assumed and if the discharge time constants are properly chosen, electric and magnetic field wave shapes calculated with the model exhibit all the significant characteristics of measured fields. From a comparison of calculated and measured field wave shapes, we find a ratio of the breakdown time constant to the channel-base current rise time between 1 and 5. Comparison of typical characteristics of field wave shapes from natural and from artificially initiated (triggered) lightning indicates a faster discharging process for triggered lightning. Depending on the breakdown time constant, the return stroke speed determined using the well-known formula for the transmission-line model, with inputs being the peak electric field and peak current from the present model, are in the range from about 50 percent to 90 percent of the return stroke speed assumed in the present model. The corresponding transmission-line model speeds determined from the peak derivatives of the electric field and current are in the range from about 140 percent to 160 percent of the assumed return stroke speed. These results supply some indication of why transmission-line model speeds determined from the ratio of measured peak current and field derivatives in triggered lightning are greater than the speeds determined from the ratio of measured peak currents and fields. For a given channel-base current, the initial peak electric field and field derivative derived from the model increases as the height above ground of the strike point increases. The new model can therefore explain the differences in the data obtained from the triggered lightning studies at Kennedy Space Center in 1985 and in 1987 as being due to the different height of the triggering structures in those two years. If natural lightning strikes an elevated object, the increase of the initial electric field and field derivative can result in an additional substantial error in determining the peak current and peak current derivative from the transmission-line model.
TL;DR: A review of the theoretical concepts and models describing the acceleration of auroral particles can be found in this article, where the dynamics of the particles are described, beginning with the adiabatic motions of particles in the converging geomagnetic field in the presence of parallel potential drops.
Abstract: The auroral zone ionosphere is coupled to the outer magnetosphere by means of field-aligned currents. Parallel electric fields associated with these currents are now widely accepted to be responsible for the acceleration of auroral particles. This paper will review the theoretical concepts and models describing this coupling. The dynamics of auroral zone particles will be described, beginning with the adiabatic motions of particles in the converging geomagnetic field in the presence of parallel potential drops and then considering the modifications to these adiabatic trajectories due to wave-particle interactions. The formation of parallel electric fields can be viewed both from microscopic and macroscopic viewpoints. The presence of a current carrying plasma can give rise to plasma instabilities which in a weakly turbulent situation can affect the particle motions, giving rise to an effective resistivity in the plasma. Recent satellite observations, however, indicate that the parallel electric field is organized into discrete potential jumps, known as double layers. From a macroscopic viewpoint, the response of the particles to a parallel potential drop leads to an approximately linear relationship between the current density and the potential drop. The currents flowing in the auroral circuit must close in the ionosphere. To a first approximation, the ionospheric conductivity can be considered to be constant, and in this case combining the ionospheric Ohm's Law with the linear current-voltage relation for parallel currents leads to an outer scale length, above which electric fields can map down to the ionosphere and below which parallel electric fields become important. The effects of particle precipitation make the picture more complex, leading to enhanced ionization in upward current regions and to the possibility of feedback interactions with the magnetosphere. Determining adiabatic particle orbits in steady-state electric and magnetic fields can be used to determine the self-consistent particle and field distributions on auroral field lines. However, it is difficult to pursue this approach when the fields are varying with time. Magnetohydrodynamic (MHD) models deal with these time-dependent situations by treating the particles as a fluid. This class of model, however, cannot treat kinetic effects in detail. Such effects can in some cases be modeled by effective transport coefficients inserted into the MHD equations. Intrinsically time-dependent processes such as the development of magnetic micropulsations and the response of the magnetosphere to ionospheric fluctuations can be readily treated in this framework. The response of the lower altitude auroral zone depends in part on how the system is driven. Currents are generated in the outer parts of the magnetosphere as a result of the plasma convection. The dynamics of this region is in turn affected by the coupling to the ionosphere. Since dissipation rates are very low in the outer magnetosphere, the convection may become turbulent, implying that nonlinear effects such as spectral transfer of energy to different scales become important. MHD turbulence theory, modified by the ionospheric coupling, can describe the dynamics of the boundary-layer region. Turbulent MHD fluids can give rise to the generation of field-aligned currents through the so-called α-effect, which is utilized in the theory of the generation of the Earth's magnetic field. It is suggested that similar processes acting in the boundary-layer plasma may be ultimately responsible for the generation of auroral currents.
TL;DR: A set of magnetic stimulus coils with different field profiles were used to isolate movement of single digits at motor threshold and to calculate corresponding electric field strengths at various distances beneath the scalp to estimate the depth of stimulation.
Abstract: Magnetic stimulation of the human brain is performed in clinical and research settings, but the site of activation has not been clearly localized in humans or other species. We used a set of magnetic stimulus coils with different field profiles to isolate movement of single digits at motor threshold and to calculate corresponding electric field strengths at various distances beneath the scalp. Two coils could produce the same electric field intensity at only 1 point. Thus, we could estimate the depth of stimulation by finding the intersection of the electric field plots, which were then superimposed on MRIs of the underlying brain. In each of 3 subjects the field plots intersected at the crown of a gyrus, in the region of the central sulcus, an near the level of the gray-white junction. This position and the electric field orientation support localization to layer VI of cerebral cortex.
Journal Article•
TL;DR: In this paper, the Rice convection model was used to study the relationship between plasmaspheric electric field perturbations and high latitude currents during disturbed periods, and it was predicted that the penetration of high latitude electric fields to low latitudes should, in general, be closely related to the rate of motion of the shielding layer and the equatorward edge of the diffuse aurora.
Abstract: F-region incoherent scatter radar drift observations from Millstone Hill and Jicamarca, h-prime F observations from Huancayo, and high latitude ground-magnetometer measurements taken during the Sundial 1986 campaign are used to study the relationship between plasmaspheric electric field perturbations and high latitude currents during disturbed periods. The observations are in good agreement with numerical results from a Rice Covection Model run that involved a sharp increase in the polar cap potential drop followed by a subsequent decrease. The zonal disturbance electric field pattern is latitude independent, and the corresponding amplitudes change approximately as L exp n (where n is about 1.5). The meridional electric field patterns and amplitudes have larger latitudinal variations. The mid-, low, and equatorial electric fields from the Rice Convection Model are in good agreement with previous results from the semianalytic, Senior-Blanc (1987) model. Also discussed are three physical mechanisms (over-shielding, fossil winds, and magnetic reconfiguration) that contribute to the long lasting (1-2 h) equatorial zonal electric field perturbations associated with a sudden northward turning of the IMF. It is predicted that the penetration of high latitude electric fields to low latitudes should, in general, be closely related to the rate of motion of the shielding layer and the equatorward edge of the diffuse aurora.
01 Jan 1990
TL;DR: In this article, the electrical and dielectric properties of tissue over a wide range of frequencies were described by using the two properties relative permittivity, ∈′ (the charge) and conductivity, σ (current densities set up in response to an applied electric field of unit amplitude).
Abstract: This chapter discusses the electrical and dielectric properties of tissue, covering the frequency range from d.c. to over 10 GHz. The electrical character of tissues over a wide range of frequencies may be described by using the two properties relative permittivity, ∈′ (the charge) and conductivity, σ (current densities set up in response to an applied electric field of unit amplitude). From both of these, the complex relative permittivity, ∈*, can be defined by the equation ij , characterize the effect in terms of the charge generated for unit applied stress under short circuit conditions.
TL;DR: In this article, a particle-in-cell simulation is used to model the plasma generated in a parallel plate RF reactor at low pressure, where the electric field and particle motion are obtained by finite-difference methods leading to the selfconsistent creation of sheaths on the boundaries.
Abstract: A particle-in-cell simulation is used to model the plasma generated in a parallel plate RF reactor at low pressure. Nonperiodic boundary conditions are used, and the electric field and particle motion are obtained by finite-difference methods leading to the self-consistent creation of sheaths on the boundaries. Model cross sections are used to describe collisions between particles. Ionization is included, and the plasma is maintained by fast electrons generated in the RF sheaths. Most of the power dissipation is due to the acceleration of ions in the time-average sheath fields. At high applied voltage, the power dissipation is described well by the power law P varies as V/sup 5/2/. Simple scaling laws for the density and plasma potential are obtained. The effect of ion mass and charge-exchange colisions on the ion energy spectrum collected by the electrodes is examined. The ion loss rate drops in the presence of charge-exchange collisions, and this leads to an increase in the density. The collisions also markedly alter the ion energy distribution function. >
TL;DR: The good fit of these data to the curves calculated using the Schwan Equation indicates that the equation may be used to describe the transmembrane potential of a living cell generated by an oscillating electric field.
TL;DR: In this paper, the authors reported the first direct demonstration of a strain-generated built-in electric field in a (111) oriented strained-layer heterostructure, where the misfit strain in a lattice mismatched quantum well was exploited to generate a longitudinal electric field via the piezoelectric effect.
Abstract: We report the first direct demonstration of a strain‐generated built‐in electric field in a (111) oriented strained‐layer heterostructure. We present a model which describes the accommodation of the misfit strain in a lattice‐mismatched quantum well, and the resulting generation of a longitudinal electric field via the piezoelectric effect. On a (111)B GaAs substrate, we grew the quantum well in the intrinsic region of a p‐i‐n diode such that the strain‐generated electric field in the quantum well opposes the weaker built‐in electric field of the diode. Under reverse bias operation, photoconductivity measurements show a quadratic blue shift of the quantum well electroabsorption peaks, in contrast to the red shifts normally observed in the quantum‐confined Stark effect. The measured blue shifts demonstrate an electric field strength of 1.7×105 V/cm, which agrees with theory to within the accuracy of the measured sample characteristics.
TL;DR: A simple closed-form analytic expression for the heavy-ion reactionCross section, involving nuclear densities of colliding ions and the nucleon-nucleon cross section, has been obtained within the framework of the Glauber model modified for the Coulomb field effect.
Abstract: A simple closed-form analytic expression for the heavy-ion reaction cross section, involving nuclear densities of colliding ions and the nucleon-nucleon cross section, has been obtained within the framework of the Glauber model modified for the Coulomb field effect. Reaction cross sections for a large number of heavy-ion systems have been predicted reasonably well over an energy range beginning with the Coulomb barrier to a few GeV/nucleon.
TL;DR: In this article, simultaneous measurements of electromagnetic fields and particle distributions, measured during the crossing by the Swedish spacecraft Viking of an auroral kilometric radiation (AKR) source, are presented.
Abstract: Simultaneous measurements of electromagnetic fields and particle distributions, measured during the crossing by the Swedish spacecraft Viking of an auroral kilometric radiation (AKR) source, are presented. It is shown that AKR is generated within an acceleration region characterized by an upward directed parallel electric field, as evidenced by its signature on the proton and electron distributions. From particle observations inside the AKR source it is clear that the potential drop below the spacecraft produces upward moving field-aligned ion beams and a depletion in the density of low energy electrons. The potential drop above the spacecraft produces downward accelerated electrons. A large fraction of these electrons have small parallel velocities; they mirror above the ionosphere. These trapped electrons lie in a region of velocity space which should be empty in a simple adiabatic theory. The authors suggest that these electrons get trapped when they experience a time-varying (or space-varying) parallel electric field. This conclusion is supported by the comparison between the observed electron distribution function and a model distribution function built by applying Liouville theorem. Since trapped electrons can cause positive gradients ({partial derivative}f{sub e}/{partial derivative}V{sub {perpendicular}} > 0) over a broad range of parallel velocities, around v{sub {parallel}} {approx} 0,more » it is suggested that they are the free energy source for the AKR. This conclusion is substantiated by an evaluation of the convective growth rate, where the various input parameters have been determined by fitting particle data.« less
TL;DR: In this article, the electric field obtained from the oscillations is in agreement with that derived from electrostatic calculations, and the Fermi level on the bare surface of AlGaAs with different Al mole fraction has also been determined.
Abstract: Franz–Keldysh oscillations from GaAs and AlGaAs structures have been studied and we find that the electric field obtained from the oscillations is in agreement with that derived from electrostatic calculations. Our results show that illumination from pump and probe beams in a normal photoreflectance experiment can significantly affect the measurement and thus erroneously lead to a reduced value of the electric field. The Fermi level on the bare surface of AlGaAs with different Al mole fraction has also been determined.
01 Jan 1990
TL;DR: A meta-modelling system that automates the very labor-intensive and therefore time-heavy and expensive and therefore expensive and expensive process of converting an electric field to a non-volatile energy resource is proposed.
Abstract: PERSPECTIVE AND OVERVIEW 83 PULSED ELECTRIC FIELD METHOD.. .. ... ........ 85 ELECTROPORATION AND ELECTROFUSION OF CELL MEMBRANES .... 87 ELECTROCONFORMATIONAL CHANGES ..... ........ ...... ....... ....... .. 89 ELECTRIC-FIELD-INDUCED Na+, K+, AND Rb+ PUMPING BY Na,K-ATPase 91 ATP SYNTHESIS INDUCED B Y ELECTRIC FIELDS 93 ENERGETICS OF ELECTRIC FIELD INTERACTION WITH A CHEMICAL EQUILIBRIUM.. ... ........ ... 95 ENFORCED CONFORMATIONAL OSCILLATION FOR ENERGY TRANSDUCTION 97 MODULATION OF A STATIONARY TRANSMEMBRANE ELECTRIC FIELD 98 MICHAELIS-MENTEN ENZYME, ENERGY, AND SIGNAl. TRANSDUCTIONS.. 101 ELECTRIC SIGNALS AND ELECTRIC NOISES.... ... ... 102
TL;DR: In this paper, the real time dynamics of a moving charged soliton in polyacetylene is studied numerically by using Su-Schrieffer-Heeger's model, where an electric field is introduced to the system through a time dependent vector potential which can be included into the Hamiltonian through the Peierls substitution of the phase factor to the transfer integral.
Abstract: Real time dynamics of a moving charged soliton in polyacetylene is studied numerically by using Su-Schrieffer-Heeger's model. An electric field is introduced to the system through a time dependent vector potential which can be included into the Hamiltonian through the Peierls substitution of the phase factor to the transfer integral. Several interesting properties of the moving soliton are obtained, e.g. , the Brownian-like motion of the soliton due to the soliton-phonon interaction, the saturation of the soliton velocity, the saturation velocity being independent of the applied electric field strength, while the time needed to attain the saturation velocity is, roughly speaking, linearly dependent on the logarithm of the applied field.
TL;DR: In this paper, a particle model of energetic electron transport in sputtering magnetron discharges is presented, which assumes time-independent magnetic and electric fields and supposes that scattering by neutral atoms is the dominant transport mechanism.
Abstract: A particle model of energetic electron transport in sputtering magnetron discharges is presented. The model assumes time‐independent magnetic and electric fields and supposes that scattering by neutral atoms is the dominant transport mechanism. Without scattering, we find that some orbits are confined indefinitely. Using the differential cross sections for elastic, excitation, and ionization collisions in argon, we perform a Monte Carlo simulation of the electrons emitted by ion bombardment of a planar magnetron cathode to predict the spatial distribution of ionization. We find good agreement with experimental measurements of the radial profile of ion flux to the cathode and of the axial profile of optical emission.
TL;DR: The algorithm given here offers a useful tool in understanding the mechanism of light absorption in various spectroscopic methods, and is convenient to use where intensity of the IR spectrum is of interest.
Abstract: A new algorithm has been proposed for the calculation of the electric field intensity in stratified multilayered films when light is incident on the system. The algorithm utilizes matrix formulas based on Abeles’s formulas for the calculation of reflectance and transmittance. Equations for calculating patial absorptance due to a certain depth in the films are also derived. Some examples of the application of the electric field description are given for the analysis of three kinds of reflection spectroscopic methods which use metal surfaces: reflection–absorption, surface electromagnetic wave, and metal overlayer ATR methods. The algorithm given here offers a useful tool in understanding the mechanism of light absorption in various spectroscopic methods, and is convenient to use where intensity of the IR spectrum is of interest.
TL;DR: A mathematical model is presented that predicts the electric field induced in the arm during magnetic stimulation of a peripheral nerve, and these results are consistent with many experimental observations in the literature, and aid in the basic understanding of Magnetic stimulation of the peripheral nervous system.
Abstract: A mathematical model is presented that predicts the electric field induced in the arm during magnetic stimulation of a peripheral nerve. The arm is represented as a homogeneous, cylindrical volume conductor. The electric field arises from two sources: the time-varying magnetic field and the accumulation of charge on the arm surface. In magnetic stimulation both of these contributions are significant. The magnitude of the electric field is greatest near the surface of the arm, and is well localized. Various coil orientations are examined; the smallest electric fields are induced when the coil is perpendicular to the arm surface, the largest when the coil is parallel. These results are consistent with many experimental observations in the literature, and aid in the basic understanding of magnetic stimulation of the peripheral nervous system.
TL;DR: In this article, a general method for the implementation of polarization in molecular dynamics simulations of small molecules is suggested, where the induction is treated explicitly, while the higher order contributions, the polarization due to induced dipoles, are taken into account in an average way by modification of potential parameters.
Abstract: A general method is suggested for the implementation of polarization in molecular dynamics simulations of small molecules. Induced dipole moments are evaluated on selected polarizability centers and represented by separation of charges. The positive polarization charges reside on the selected atoms. The negative polarization charges are treated as additional particles. The positions of these polarization charges are determined from the electrical fields due to the permanent charges of the system. Thus the induction is treated explicitly, while the higher order contributions, the polarization due to induced dipoles, are taken into account in an average way by modification of potential parameters. The forces can be evaluated for the new charge distribution in the conventional way. As an illustration of this approach initial results are reported for the development of a polarizable water model. The higher order polarization is treated in an average way by slight increase of the permanent charges as ...
TL;DR: In this article, the role of dc electric fields in the acceleration of the Swedish satellite Viking has been investigated and it has been shown that magnetic-field-aligned potential drops play an important role in auroral acceleration.
Abstract: Electric field measurements on the Swedish satellite Viking have confirmed and extended earlier observations on S3-3 and provided further evidence of the role of dc electric fields in auroral acceleration processes. On auroral magnetic field lines the electric field is strongly fluctuating both transverse and parallel to the magnetic field. The significance of these fluctuations for the auroral acceleration process is discussed. A definition of dc electric fields is given in terms of their effects on charged particles. Fluctuations below several hertz are experienced as dc by typical auroral electrons if the acceleration length is a few thousand kilometers. For ions the same is true below about 0.1 Hz. The magnetic-field-aligned (as well as the transverse) component of the electric field fluctuations has a maximum below 1 Hz, in a frequency range that appears as dc to the electrons but not to the ions. This allows it to cause a selective acceleration, which may be important in explaining some of the observed characteristics of auroral particle distributions. The electric field observations on Viking support the conclusion that magnetic-field-aligned potential drops play an important role in auroral acceleration, in good agreement with particle observations boht on Viking and on the DEmore » satellites. They also show that a large part, or even all, of the accelerating potential drop may be accounted for by numerous weak (about a volt) electric double layers, in agreement with earlier observations on the S3-3 satellite and with an early theoretical suggestion by L. Block.« less